The Economic Domain
The basis of economic modeling lies in the hard data on inputs and outputs and how to connect them. Static or dynamic input-output models are the closest to these sets of basic data. These models seem to be well fitted to connect the economic to the environmental domain by means of expressing both financial and material flows through the economy.

The Ecological Domain
The past ten years have witnessed the rapid development of a new approach called 'integrated environmental assessment modeling for describing the anthropogenic and natural impacts on the environment and the earth system. Most of the global environmental integrated assessment models (EIAMs) focus on climate change. Gradually other features are added to these models to cover the broader perspective of global change. The current state of development on EIAMs is still far from the target of complete integration of natural systems and processes.

The Social Domain
The geographical distribution of the population, and changes of this distribution, is interwoven with many dimensions of development. At the social level, a limited number of demography and human health modeling approaches are available, which include an integrated approach of both fertility and mortality processes in relation to socio-economic and environmental conditions. These types of models are able to reproduce the human development and poverty indices as proposed by UNDP and may support the UN population prognosis.

The Institutional Domain
Modeling social institutions is in its early stages of development. It is speculated that social sciences may not yield simple and powerful generalizations dealing with the roles of institutions in causing and confronting large-scale environmental changes. Several conceptual models have been developed linking global environmental change to violent conflict and failure of institutions. These models link the quantity and quality of natural resources, the access to these resources and population growth through environmental scarcity, migration and decreased economic activity to weakened states and related conflicts.

Integrating the Four Dimensions of Sustainability
The use of formal assessment methodologies is limited, due to the fact that our knowledge about the domains involved is often limited. The complexity of these domains may increase if human behavior gains importance. Another scientific problem is the choice of levels of aggregation in time and space in the assessment process. Two main aspects are important in the integration of the domains of sustainability: optimality and durability. The assessment system to be developed may therefore consist of three layers connected to each other in the following way:

a basic layer of data from monitoring systems, exogenous inputs like scenario's and pre-run results of detailed models,

a second layer consisting of independent expert models for priority issues, to be run separately, fed by the layer of basic data;

a third layer of linked meta-models in which the expert models are represented by simplified images ( the meta-models).